1. Field of Invention
The present invention generally relates to a heating device for a fluid line, in particular for a crankcase venting system in an internal combustion engine, with a heating element and with a holding device, through which the heating element can be mounted on the fluid line. The invention also relates to a fluid line for the accommodation of the said heating device and to a heating module with a fluid line and a heating device fitted to it. Finally, the invention also relates to a method for the manufacture of the heating device mentioned above.
2. Description of the Related Art
In modern internal combustion engines, vents are provided for the crankcase which houses the crank mechanism with the crankshaft, the connecting rods and the pistons as well as the cylinders. The crankcase is sealed on the cylinder side by one or more cylinder heads and underneath a sump pan is normally joined to the crankcase.
When the internal combustion engine is operated, the crankcase fills up to the cylinder head with oil vapours and gases which leak out of the combustion chamber in the cylinders past the piston rings. These oil vapours and gases are also known as blow-by gases. Due to the pumping motion of the pistons, the blow-by gases are subjected to pressure. Since the oil vapours and gases in the crankcase contain large quantities of ecologically harmful hydrocarbons, measures have to be taken to prevent the escape of the oil vapours and gases from the crankcase.
For this purpose it is known that crankcase vents can be provided which connect the internal space of the crankcase to the air intake lines of the internal combustion engine, so that the blow-by gases are sucked out of the crankcase, together with the fresh air and are burnt.
If the fresh air and the blow-by gases from the crankcase exhibit however substantially different temperatures, condensation and precipitation can take place in the mixing section, which blocks the crankcase vents.
In particular with car engines, high temperature differences arise in winter between the cold intake air on one hand and the blow-by gases from the crankcase which heat up quickly with the engine block. In some cases this can even lead to the icing up or blockage of the opening of the fluid line of the crankcase vent. With a blockage of the crankcase vent a high pressure builds up in the crankcase which can press the lubricating oil out of the seals on the crankshaft, sump pan or out of the opening for the oil dipstick. In addition, the pistons are subjected to increased work against the high pressure in the crankcase, leading to a reduction in the efficiency of the internal combustion engine.
The condensation of the gases and the precipitation of mixture constituents at low outside temperatures is avoided in the state of the art by heating devices in the lines to the crankcase vent. These types of heating devices are for example known from DE-A-2432782, U.S. Pat. No. 4,922,882, U.S. Pat. No. 5,970,962, U.S. Pat. No. 6,062,206, JP-AA-10231543, JP-M-10121937 and EP-A-1164264.
With the crankcase vent of DE-A-2432782 the opening of the venting line on the intake system can be heated electrically. For this, a heating device is used which consists of a metal tubular piece with an electrical heating conductor arranged coaxially on its jacket surface. For heating, a winding of resistance wire located on a coil bobbin is used. A disadvantage with the heating device of DE-A-2432782 is primarily the large space requirement which renders its use with modern engines almost impossible. In addition, the heating device in DE-A-2432782 is difficult to install and difficult to replace should damage occur.
U.S. Pat. No. 4,922,882 deals with a crankcase venting system which is heated via the cooling system of the internal combustion engine. For this, a ring pipe is provided surrounding the intake line and being located in the region of the feed line of the crankcase gases into the engine intake line. With very cold outside temperatures, the ring pipe is heated by the cooling system.
With the further developed heating devices of U.S. Pat. No. 5,970,962 and U.S. Pat. No. 6,062,206 a PTC (Positive Temperature Coefficient) heating element is used instead of the resistance wire. The heating element is connected for thermal conduction with a heatsink which surrounds the opening of the crankcase vent. The heatsink and the heating element are integrated into a plug which simultaneously forms the opening of the crankcase vent. Although the space requirement with the devices of U.S. Pat. No. 5,970,962 and U.S. Pat. No. 6,062,206 is less than with the heating device of DE-A-2432782, their complicated manufacture and their poor accessibility on the internal combustion engine are disadvantages during servicing.
In JP-AA-10231543, a heating device is shown with which a cylindrical, metal thermal radiator element is inserted into a through opening of a pipe. At the other end of the thermal radiator element a mounting seat is attached water-tight to a mounting seat on the pipe end. The cylindrical thermal radiator element protrudes into a flow and transfers heat from the heating device directly into the fluid in the pipe.
JP-AA-10121937 relates to a heater for blow-by gases using a PCV valve. The housing of the PCV valve is heated by a heater hose via a leaf-spring clip.
In EP-A-1164264 the PTC elements are stuck onto the fluid line for the crankcase venting by an electrically non-conducting silicone adhesive and sprayed with plastic after mounting. In this way a compact construction is achieved irrespective of the design of the fluid line. However, the heating device of EP-A-1164264 can be improved with respect to its service friendliness.
Considering the disadvantages of the state of the art of known heating devices, it is desirable to improve a heating device for fluid lines, in particular for crankcase vents of internal combustion engines, such that with a compact construction they are more convenient for servicing and are easier to install.